/Engine/Source/Developer/TextureFormat/Public/ChildTextureFormat.h
Gets an optional derived data key string, so that the compressor can rely upon the number of mips, size of texture, etc, when compressing the image
A string that will be used with the DDC, the string should be in the format "_"
virtual [FString](API\Runtime\Core\Containers\FString) GetDerivedDataKeyString ( const [FTextureBuildSettings](API\Developer\TextureCompressor\FTextureBuildSettings) & InBuildSettings, int32 InMipCount, const FIntVector3 & InMip0Dimensions ) const